An IC module is a semiconductor device in which: an IC (integrated circuit) chip is electrically connected to a substrate such as a print wiring substrate, and a terminal for allowing electrical connection with outside is provided on the print wiring substrate so as to be positioned on a back surface of a surface having the IC chip.
FIG. 9 is a cross sectional view schematically showing a general IC module.
As shown in FIG. 9, generally, an IC module is arranged so that: one surface of an insulating support substrate 101 (substrate such as a print wiring substrate or the like) includes contact terminals 102 (electrical connection terminal), functioning as connection terminals for allowing connection with outside, each of which is constituted of an input/output contact terminal capable of external access, and the other surface of the insulating support substrate 101 includes an IC chip 103. The contact terminals 102 and terminals of the IC chip 103 are connected to each other via through holes 104 provided in the insulating support substrate 101, wiring patterns (not shown) provided on the insulating support substrate 101, and the like, so that the contact terminals 102 and the IC chip 103 are electrically connected to each other.
The IC module is mounted on an IC card for example. In this manner, the IC module mounted on the IC card is always exposed to an electrostatic condition since the IC card is brought with a user as a portable device. Originally, the IC chip 103 itself provided in the IC card includes an ESD (electrostatic discharge) protection circuit, such as an electrostatic protection diode, provided on an input/output section of the IC chip 103, which functions as a protection circuit (excessive voltage protection element) for preventing electrostatic damage.
However, in case where static electricity is applied to each of the contact terminals 102 provided on a surface of the IC module exposed at a surface of the IC card, the static electricity enters into the IC chip 103 via each of the through holes 104. At this time, when strength of the static electricity is allowable for the IC chip 103, an electrostatic stress caused by the static electricity is absorbed in the IC chip 103. However, when the electrostatic strength is not allowable for the IC chip 103, it is impossible to absorb all the electrostatic stress caused by the static electricity, so that an input/output terminal (not shown) of the IC chip 103 is damaged or broken.
The following description explains a structure of the contact terminal 102 of the IC module.
A module terminal of a contact-type IC card is defined under ISO7816. FIG. 10 is a plan view schematically showing a layout in which the contact terminals 102 of each module terminal of the contact-type IC card are disposed in accordance with definition of ISO7816.
As shown in FIG. 10, the module terminal of the contact-type IC card is defined under ISO7816. As shown in FIG. 10, the module terminal includes as the contact terminals 102 shown in FIG. 9: a GND terminal 204 which is a ground terminal for a reference potential; a VCC terminal 208 and a VPP terminal 203 each of which is a terminal for power source; a CLK terminal 206 which is a terminal for inputting a clock; an RST terminal 207 which is a terminal for inputting a reset signal; an I/O terminal 202 which is a terminal for inputting/outputting data; and an RFU0 terminal 201 and an RFU1 terminal 205 each of which functions as an extension input/output terminal (Reserve For User terminal). Out of the contact terminals 102 constituting the IC module, the GND terminal 204 is disposed adjacent to all the other contact terminals 102.
The layout in the module terminal of the IC card is determined under ISO7816 in this manner. However, each contact terminal 102 constituting the module terminal has an arbitrary shape.
In the IC module shown in FIG. 10, a distance d between the contact terminals 102 is uniformly 150 μm for example. However, when the distance between the contact terminals 102 is uniformed in this manner, the following disadvantage occurs. That is, in case where static electricity is applied to the contact terminal 102 and the surge discharge (electric arc) aerially occurs between the contact terminals 102 adjacent to each other before the static electricity is absorbed by the IC chip 103 (see FIG. 9) via the through hole 104, the surge discharge may occur also in the contact terminal 102 (input/output contact terminal), disposed adjacent to that contact terminal 102, which is a terminal other than the GND terminal 204. When the surge discharge is applied to the adjacent contact terminal 102 (input/output contact terminal), the surge discharge enters into the IC chip 103 via the through hole 104 of the adjacent contact terminal 102 (input/output contact terminal), so that the surge discharge may brake the IC chip.
Then, efforts are made so as to protect the input/output terminal of the IC chip 103 from the static electricity by leading the surge discharge caused by the static electricity to the GND terminal 204 in the case where the static electricity which occurs in the contact terminal 102 causes the surge discharge.
FIG. 11 is a plan view schematically showing an IC module formation portion of an IC card recited in Japanese Unexamined Patent Publication No. 146796/1989 (Tokukaihei 1-146796)(publication date: Jun. 8, 1989: hereinafter, referred to as Patent Document 1: Corresponding U.S. Pat. No. 4,942,495).
The IC module shown in FIG. 11 is arranged so that: surge discharge (electric arc) which occurs between the contact terminal 102 and another contact terminal 102 other than the GND terminal 301, i.e., between the input/output contact terminal 302 and the GND terminal 301 is promoted, and a minimum voltage required in occurrence of the surge discharge is reduced, thereby reducing an excessive voltage applied to the input/output contact terminal 302. Thus, a plurality of metal protruding portions 301a and a plurality of metal protruding portions 302a are respectively provided on the GND terminal 301 and the input/output contact terminal 302 which is the contact terminal 102 other than the GND terminal 301, thereby reducing a shortest distance e between the GND terminal 301 and the input/output contact terminal 302 other than the GND terminal 301 so that the distance e is less than 100 μm.
Further, each of FIG. 12 and FIG. 13 is a plan view showing an example of a schematic arrangement of an IC module formation portion of an IC card recited in Japanese Unexamined Patent Publication No. 262081/1993 (Tokukaihei 5-262081)(publication date: Oct. 12, 1993: hereinafter, referred to as Patent Document 2).
In the IC module shown in FIG. 12, a gap f between (i) an input/output contact terminal 402 sending a surge discharge (electric arc) component and (ii) a GND terminal which functions as an input/output contact terminal 402 receiving the surge discharge (electric arc) component is set to be uniformly narrower than a gap g between input/output contact terminals 402, disposed adjacent to each other, which are terminals other than the GND terminal 401.
Further, an IC module shown in FIG. 13 is arranged so that: a protruding portion 402a is provided on a side face, included in an input/output contact terminal 402, which is positioned opposite to a side face of an extended portion 401a of a GND terminal 401 functioning as an input/output contact terminal 402 receiving the surge discharge (electric arc) component, thereby setting a gap h between the protruding portion 402a and the extended portion 401a of the GND terminal 401, i.e., a gap between the GND terminal 401 and the input/output contact terminal 402 other than the GND terminal 401, to be narrower than a gap g between the input/output contact terminals 402, disposed adjacent to each other, which are terminals other than the GND terminal 401.
However, the Patent Document 1 gives no consideration for an impulse current component contained in the surge discharge (electric arc) component which occurs between the contact terminals 102 other than the GND terminal 301.
A distance between the contact terminals 102 of the IC module is generally several hundreds μm (for example, 150 μm in FIG. 10). When electric field intensity caused by static electricity which occurs in the contact terminal 102 exceeds dielectric strength (breakdown voltage) of air which exists between the contact terminal 102 and another contact terminal 102 adjacent to that contact terminal 102, the surge discharge occurs. It is known that the breakdown voltage of air is approximately 100 kV/cm. When static electricity applied to the contact terminal 102 reaches electric field intensity over approximately 100 kV/cm, the static electricity is discharged toward the adjacent contact terminal 102 as the surge discharge (electric arc).
A demonstration experiment demonstrates that the surge discharge component contains a special impulse current component which is approximately three times as strong as general electrostatic strength in a human body model (HBM).
Thus, when the surge discharge component occurs, the electrostatic strength exerted to the adjacent contact terminal 102 is higher than the electrostatic strength in case where the static electricity is applied directly to the IC module. When an excessive voltage protection element (ESD protection circuit) provided in a general IC chip 103 cannot allow the special impulse current component, the IC chip 103 is damaged or broken.
The Patent Document 1 aims to protect the circuit by intentionally causing the surge discharge (electric arc) component. Thus, the plurality of metal protruding portions 301a and the plurality of metal protruding portions 302a are respectively provided on the GND terminal 301 and the input/output contact terminal 302 other than the GND terminal 301 as described above, thereby reducing a shortest distance e between the GND terminal 301 and the input/output contact terminal 302 other than the GND terminal 301. Therefore, in the IC module recited in the Patent Document 1, when the static electricity occurs in the GND terminal 301, also the surge discharge from the GND terminal 301 to the input/output contact terminal 302 other than the GND terminal 301 is likely to occur.
Thus, in the IC module recited in the Patent Document 1, the IC chip 103 (see FIG. 9) repeatedly receives the impulse current component every time the static electricity occurs in the IC module.
That is, in the IC card recited in the Patent Document 1, the plurality of metal protruding portions 301a and the plurality of metal protruding portions 302a are respectively provided on the GND terminal 301 and the input/output contact terminal 302, that are provided on a surface of the IC card, with the metal protruding portions 301a and 302a positioned opposite to each other. Thus, the surge discharge occurs between each metal protruding portion 301a and each metal protruding portion 302a on the surface of the IC card. Moreover, there is no telling which one of the metal protruding portions 301a and 302a the surge discharge (electric arc) component is transmitted to. Since the IC card is brought with a user, as a portable device, the surge discharge occurs in the surface of the IC card several times depending on a condition under which the IC card is used. Thus, the impulse component contained in the surge discharge (electric arc) may cause wirings and the like provided on the insulating support substrate 101 (see FIG. 9) to be burned out.
Further, in a general withstand electrostatic voltage strength evaluation test), there are two types of the test: the test is carried out in terms of a GND terminal basis (the GND terminal is connected to a GND potential of an evaluation apparatus (the GND terminal is grounded)) and the test is carried out in terms of a VCC basis (a VCC terminal is connected to the GND potential of the evaluation apparatus (the VCC terminal is grounded)). In case of the latter, it is highly probable that: in the module structure of the Patent Document 1 arranged so as to intentionally cause the surge discharge, static electricity which occurs in the GND terminal 301 facilitates occurrence of the surge discharge which occurs from the GND terminal 301 to another contact terminal 102 adjacent to the GND terminal 301.
Taking into consideration the impulse current component contained in the surge component in this manner, the structure of the IC module recited in the Patent Document 1 is not effective in protecting the IC chip from the ESD.
Further, high accuracy is required in processing the plurality of metal protruding portions so that a terminal distance therebetween is less than 100 μm, and this causes productivity to drop. Moreover, the metal protruding portions 301a and the metal protruding portions 302a are respectively provided on a surface opposite to the GND terminal 301 and the input/output contact terminal 302 other than the GND terminal 301, and each of the metal protruding portions 301a and 302a is extremely small, so that electric fields are likely to gather in an end (end of the protruding portion) of each of the metal protruding portions 301a and 302a at the time of the surge discharge. As a result, the end of the protruding portion tends to be damaged.
As described above, the IC card is used as a device brought with the user as a portable device, so that its reliability is required to be higher than other conventional IC cards. Thus, it is considered that: a shape of each input/output contact terminal 302 of the IC module recited in the Patent Document 1 is disadvantageous in using the IC card.
Meanwhile, the IC module recited in the Patent Document 2 is arranged so that: the GND terminal 401 is formed in a straight line pattern, so that a gap between the GND terminal 401 and the input/output contact terminal 402 other than the GND terminal 401 is set to be narrower than a gap between the input/output contact terminals 402, disposed adjacent to each other, which are terminals other than the GND terminal 401, without forming a protruding portion on the GND terminal 401 unlike Patent Document 1. Thus, according to the Patent Document 2, when static electricity is applied to the input/output contact terminal 402, it is possible to preferentially lead the surge discharge caused by the static electricity to the GND terminal 204.
However, in the input/output contact terminal 402 of the Patent Document 2, the GND terminal 401 is formed in a straight line pattern, so that each side face of the extended portion 401a of the GND terminal 401 has a straight line shape. Thus, when the IC card is bent, a mechanical stress is exerted to the gap between the GND terminal 401 and the input/output contact terminal 402 other than the GND terminal 401. This is likely to result in chip breakage.
Further, each of the Patent Document 1 and the Patent Document 2 gives no consideration for the surge discharge in case where a non-connection terminal (hereinafter, referred to as NC terminal) is provided as a reserve terminal (preparatory terminal).
That is, in FIG. 10, it is necessary to completely disconnect some contact terminals 102 constituting the IC module, that is, the RFU0 terminal 201, the RFU1 terminal 205, each of which is an extension input/output terminal, and the VPP terminal 203 for data writing power source, from the IC chip 103, depending on specifications of the IC module, so as to make the foregoing contact terminals 102 completely in an electrically floating state.
In case where the NC terminal is provided on the surface of the IC module as the contact terminal 102 (see FIG. 9), the static electricity applied to the NC terminal is not absorbed by the IC chip 103, and all the static electricity is applied to air between the NC terminal and the contact terminal 102 adjacent to the NC terminal.
When the static electricity applied between the NC terminal and the contact terminal 102 adjacent to the NC terminal reaches electric field intensity over approximately 100 kV/cm which is a breakdown voltage of air, the surge discharge (electric arc) occurs from the NC terminal to the contact terminal 102 adjacent to the NC terminal.
Thus, the surge discharge from the NC terminal is more likely to occur than the surge discharge which occurs from other contact terminal 102.
As described above, it is apparent that the surge discharge component contains a special impulse current component which is approximately three times as strong as general static electricity of a human body model (HBM). Thus, when the surge discharge (electric arc) component occurs from the NC terminal, the electrostatic strength exerted to the adjacent contact terminal 102 is higher than the electrostatic strength in case where the static electricity is applied directly to the IC module. In case where an excessive voltage protection element provided in a general IC chip 103 cannot allow the special impulse current component, the IC chip 103 is damaged or broken.
Therefore, an effective withstand voltage against the static electricity of the IC module having the NC terminal may be lower than an IC module having no NC terminal. When the NC terminal is provided on the IC module, the IC chip is more likely to be damaged or broken than the IC module having no NC terminal.
Generally, a distance between the contact terminals 101 provided on the surface of the IC module is several hundreds μm (for example, 150 μm in FIG. 10). Since electrostatic charge on a human body reaches several kV and the NC terminal is completely in an electrically floating state, there is no discharge path for discharging the static electricity applied to the NC terminal to the IC chip 103, and the static electricity gathers in air between the NC terminal and the adjacent contact terminal 102. In terms of these conditions, it can be said that: the surge discharge (electric arc) component discharged from the NC terminal to which the static electricity has been applied is highly likely to influence the contact terminal 102 adjacent to the NC terminal.
Particularly, the IC module shown in FIG. 10 is arranged so that: the distance between the contact terminals 102 is uniformed, and the NC terminal constitutes a protruding pattern 209 which protrudes toward the contact terminal 102 adjacent thereto, thereby accelerating the surge component to the adjacent contact terminal 102. Therefore, in the IC module having the structure shown in FIG. 10, when the NC terminal is provided, the surge discharge component discharged from the NC terminal is highly likely to be applied not to the GND terminal but to the contact terminal 102. Thus, it can be said that the IC chip is highly likely to be damaged or broken by the special impulse current component contained in the surge discharge component.